title: Down-regulation of the myo-inositol oxygenase gene family has no effect on cell wall composition in Arabidopsis.
abstract: The enzyme myo-inositol oxygenase (MIOX; E.C. 1.13.99.1) catalyzes the ring-opening four-electron oxidation of myo-inositol into glucuronic acid, which is subsequently activated to UDP-glucuronic acid (UDP-GlcA) and serves as a precursor for plant cell wall polysaccharides. Starting from single T-DNA insertion lines in different MIOX-genes a quadruple knockdown (miox1/2/4/5-mutant) was obtained by crossing, which exhibits greater than 90% down-regulation of all four functional MIOX genes. Miox1/2/4/5-mutant shows no visible phenotype and produces viable pollen. The alternative pathway to UDP-glucuronic acid via UDP-glucose is upregulated in the miox1/2/4/5-mutant as a compensatory mechanism. Miox1/2/4/5-mutant is impaired in the utilization of myo-inositol for seedling growth. The incorporation of myo-inositol derived sugars into cell walls is strongly (>90%) inhibited. Instead, myo-inositol and metabolites produced from myo-inositol such as galactinol accumulate in the miox1/2/4/5-mutant. The increase in galactinol and raffinose family oligosaccharides does not enhance stress tolerance. The ascorbic acid levels are the same in mutant and wild type plants.
authors.affiliation: Department of Cell Biology, Plant Physiology, University of Salzburg, Hellbrunnerstr. 34, 5020 Salzburg, Austria.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Endres
authors.forename: Raimund
authors.initials: R
authors.lastname: Tenhaken
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D053898:Biosynthetic Pathways; D002473:Cell Wall / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D014644:Genetic Variation; D005965:Glucuronates / Q000096:biosynthesis; D007294:Inositol / Q000378:metabolism; D050562:Inositol Oxygenase / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005965:Glucuronates; D007294:Inositol; D050562:Inositol Oxygenase